1. Field of the Invention
The present invention relates to a magnetic tape cassette. More particularly, it relates to an improvement of a tape clamp of a reel for winding a magnetic tape.
2. Description of the Prior Art
As shown in FIG. 1, the magnetic tape cassette comprises a cassette casing formed by two half cases (1), (2) and a magnetic tape (3) and rotatable (4), (4) for winding the magnetic tape (3) which are held in the casing and sheets (5), (6) which are respectively placed between the inner wall surfaces (1a), (2a) of the half cases (1), (2) and the reels (4), (4) on which the magnetic tape is wound.
As shown in FIG. 2 (A) and (B), the reels (4), (4) are respectively formed by a reel substrate (7) and a jaw (8) and a tape clamping member (9) which is detachably fitted to the reel substrate (7), thereby forming a circular magnetic tape wound surface.
A leader part or a trailer part (3a) of the magnetic tape (3) is held between contacting surfaces of the reel substrate (7) and the tape clamping member (9) under the high mutual pressure of them.
Thus, in the conventional reel (4), an exterior angle .alpha. between a line extending from D.sub.1 of a contact surface of the jaw (8) and an axial line E.sub.1 for dividing the tape clamping member (9) into two half parts is an obtuse angle which is larger than a right angle (90 degrees). Therefore, the clamping force on the contact surface D.sub.1 of the jaw (8) is not high enough. As shown in FIG. 2B, when a certain clamp releasing force F.sub.1 to the radial direction is applied to the tape clamping member (9), the contact surface of the jaw (8) slips in the radial direction so as to be easily detached.